The invention relates generally to energy storage and management systems.
Electric vehicle propulsion systems use rechargeable traction batteries to provide electric power for driving electric motors coupled in driving relationship to wheels of the vehicles. Hybrid electric vehicle propulsion systems additionally include internal combustion engines to drive on-board generators to supplement battery power. Hybrid locomotive applications typically require about 200 kWhr (kilo Watt hours) to about 1000 kWhr of energy storage and the ability to handle peak power of about 2 MW (mega Watts) to about 5 MW. As specific power goals, specific energy goals, and energy storage costs are increasing, locomotive manufacturers are further challenged by design life cycles of twenty years coupled with severe environmental conditions such as shock/vibration and widely varying temperatures.
Uninterruptible power supply applications require energy storage technology to meet high specific power and moderately high specific energy specifications. Conventional flywheels have reasonably high specific power ranging from about 200 W/kg (Watts per kilogram) to about 2000 W/kg. Several recently designed flywheels include high strength composite materials that allow light-weight flywheel rotors to spin at speeds in excess of 50,000 rpm to achieve acceptable specific energy for uninterruptible power supply applications. The more recent designs have high energy storage costs (about 20,000 US dollars/kWhr to about 100,000 US dollars/kWhr) and require high levels of vacuum (on the order of about 10xe2x88x926 torr, for example) to minimize parasitic losses. Such costs are prohibitively high for locomotive embodiments.
It would therefore be desirable to provide a cost effective and robust energy storage and management system.
To provide a cost effective and robust energy storage and management system, according to one embodiment of the present invention, flywheels are used in combination with batteries and an energy storage system controller.
Briefly, in accordance with a more specific embodiment of the present invention, an energy management system comprises: an energy storage system comprising flywheels and batteries; and an energy storage system controller adapted to cause the flywheels and batteries to store energy during load-supplying periods and to supply energy during load-receiving periods.
In accordance with another embodiment of the present invention, an energy management system comprises an energy storage system comprising a vehicle platform including a plurality of compartments; a plurality of flywheels situated in respective ones of the plurality of compartments; and a plurality of batteries situated above the plurality of flywheels.